1. Field of the Invention
The present invention relates to a camera having therein a rewritable memory, and more particularly to a camera capable of being electrically connected to an external apparatus via contacts formed in the cassette chamber for writing to and reading from the memory.
2. Description of the Related Art
Most cameras have a built-in microcomputer which electrically controls the camera operation. For example, a photometric correction amount, an autofocus correction amount, a flash level, a battery check level, and the like are stored in a memory. By using such data in the memory, the microcomputer performs a correction process, an automatic flash control, a battery replacement alarm process, and the like. Recent cameras have used non-volatile memories such as an EEPROM (Electrically Erasable & Programmable ROM) to which data is rewritable.
After manufacture of a camera, the performance of the camera is tested. In accordance with this performance test, data in EEPROM is corrected to proper data. In correcting data in EEPROM, an external apparatus is connected to the microcomputer for data read/write of EEPROM.
A photographic film cassette of the type 135 has a DX code representative of film information, the code being formed at the outer surface of the cassette. This DX code is constituted by a contact pattern of conductive and nonconductive areas. A camera adapted to the type 135 has a plurality of contact pins disposed in a cassette chamber. The contact pins contact the contact patterns of a photographic film cassette to read the DX code. For data read/write of EEPROM, the microcomputer is connected to an external apparatus via the contact pins. Therefore, terminals specialized to data read/write are not necessary so that cost and compactness of cameras can be improved.
Sales of photographic film cassettes of the type IX240 started in April of 1996. The detailed structure of the photographic film cassette of type IX240 is described in U.S. Pat. Nos. 4,832,275, 4,834,306, 5,271,577 (corresponding to Japanese Patent Laid-open Publication No. 3-37645) and 5,407,146 (corresponding to Japanese Patent Laid-open Publication No. 3-37645). One feature of this photographic film cassette is that the film leader is completely housed in the cassette and advanced out of the cassette by spool rotation. Another feature is that a transparent magnetic layer is formed on the back surface of the photographic film, in which layer photographing information and print information are recorded.
The type IX240 uses a bar code disk indicating film information. The bar code disk is fixed to one end of the spool and housed in the cassette shell. The cassette shell is formed with a window for exposing the record area of the bar code. A reflection type photosensor constituted by an LED and a light receiving element is disposed at the outside of the upper wall of the cassette chamber. While the bar code disk rotates together with the spool during film advance, the reflection type photosensor reads the bar code on the bar code disk via an opening formed in the upper wall of the cassette chamber.
A camera adapted to the type IX240 is not provided with a plurality of contact pins for contact with the contact pattern. U.S. patent application Ser. No. 08/408,817 filed on Mar. 23, 1995 (presently continuation-in-part numbered U.S. Ser. No. 08/579,994) has proposed to use the bar code reading photosensor of a reflection type for data read/write of EEPROM. An external apparatus used for data read/write has a connector having the same outer dimension as the cassette. A reflection type photosensor is disposed on the top face of the connector, in correspondence with the reflection type photosensor of the camera.
This approach of using the bar code reading reflection type photosensor is advantageous in that the camera is not required to prepare optical interface for data communications. However, for data read/write of EEPROM, a signal converter is required which converts electrical signals of "0" and "1" into two types of light pulses (optical pulses) having different pulse widths. Therefore, the structure becomes complicated and the cost increases.
For data read/write of EEPROM, the microcomputer is set to a data input/output mode. This mode is set by a combination of operations of a photographing mode switch and a shutter button which can be accessed externally. Therefore, the data input/output mode may be set inadvertently by a user. In this case, if the reflection type photosensor senses external light during this mode which uses light pulses for data transfer, data in EEPROM may be changed or lost.